textproduct: Rapid City

KEY MESSAGES

- Continued warm, breezy, and mostly dry this week supporting elevated to near-critical fire weather conditions at times.

- Thunderstorm potential remains low/isolated Thursday, before increasing for Friday, Saturday, and Sunday. Pattern remains unsettled into next week.

UPDATE

Issued at 1056 PM MDT Wed May 27 2026

Very warm weather with breezy southerly winds and low chances for afternoon storms will continue through the end of the work week. Most recent CAMs are continuing to show isolated shower/storm activity over the CWA for tomorrow as a weak upper wave slides north through the CWA. Steep low level lapse rates and modest mid to upper level moisture should support convection, though buoyancy and shear will be limited (CAPE <1000 J/kg and basically no shear) which will keep chances for organized convection near zero.

DISCUSSION

(This Evening Through Wednesday) Issued at 126 PM MDT Wed May 27 2026

The synoptic pattern remains unchanged as longwave ridging over the central CONUS largely controls our weather while longwave troughing with a nearly stationary large/sprawling low pressure system spins to our west over California and Nevada. This will support continued warm temperatures and dry and breezy conditions leading to elevated to near-critical fire weather concerns each day. The forecast remains dry today, but the (albeit still low) chance of a few isolated thunderstorms has perhaps increased a touch Thursday afternoon/evening as a "tongue" of surface low pressure to our south lifts north across Nebraska and eastern Wyoming...trending a bit further north compared to yesterday's model runs, accompanied by a slight uptick in simulated reflectivity in the 12z HREF suite of CAMs. Any activity will develop in an environment devoid of shear with CAPE less than 1,000 J/kg, suggesting any isolated thunderstorms shouldn't be particularly strong and will be pulse- mode. Our potential for daily showers and thunderstorms still looks to increase quite a bit Friday, Saturday, and Sunday as the western low weakens and finally ejects/lifts northeast across the Rockies as more of an open shortwave trough, resulting in height falls and better ascent. This feature will become negatively-tilted, perhaps supporting some more robust convection as well as we get into that Friday-Sunday timeframe...long-range model soundings do suggest increasing instability/CAPE, and possibly some increase in shear especially by Saturday. Progression of the low will be slow, and will continue to support unsettled conditions/daily precip chances into the middle of next week with temperatures only slightly cooling with time. 500mb height ensemble cluster analysis universally supports continued presence of some sort of low/trough with it's center/axis still west/northwest of our CWA through at least Tuesday.

With the above in mind, largely held with NBM guidance throughout the forecast, except added low 10-20% PoPs and increased thunder probs Thursday afternoon and evening across northeast Wyoming and generally along and south of I-90 in South Dakota to introduce that chance of isolated thunderstorms. Also slightly reduced winds/wind speeds over the next 3 days as NBM guidance is coming in a bit excited, especially given S/SE flow which doesn't usually "overperform" for our area. Still, breezy conditions are expected, and gusts of 30-45 MPH will be quite common with a localized gust to 50 MPH not out of the question during peak diurnal mixing each afternoon.

AVIATION

(For the 18Z TAFS Through 18Z Friday) Issued At 1113 AM MDT Thu May 28 2026

VFR conditions are expected through most of the forecast period. Isolated showers and thunderstorms are possible across portions of northeast Wyoming, western SD, and into south-central SD. Transient MVFR conditions are possible with the showers and thunderstorms. Widespread, gusty southeasterly winds (~35kts) will persist into the evening before weakening during overnight hours.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.